Solar thermal energy system

ABSTRACT

In order to increase the efficiency of a solar thermal system, it is proposed that a measuring robot movable in the longitudinal extension, which can measure the radiance distribution directed at the receiver tube along the receiver and therefore can check if the reflectors of the system are correctly adjusted, be placed on the cover of the receiver, which is supported in a raised manner.

The present invention relates to a solar thermal energy system having aplurality of reflectors, which reflect incident sunlight onto a receivermounted in elevated manner, whereby the receiver has a receiver pipethat is overlapped by a receiver cover, and a measuring robot isdisposed on the receiver cover for measuring the beam densitydistribution of the sunlight reflected by the reflectors in the area ofthe receiver pipe.

A solar thermal energy system essentially consists of an array ofreflectors and a receiver pipe. The reflectors are directed into theincident sunlight in such a way that the sunlight is reflected by thereflectors and bundled onto the receiver. The receiver is a pipe that issurrounded by a translucent housing on its side facing away from thereflectors. A medium is conducted in the pipe, which medium is heated bythe sunlight focused onto the pipe. Because of the temperaturesresulting from this, energy can be obtained using a configuration ofthis type. Because an entire array of reflectors is used, which bundlethe incident sunlight onto the receiver, it is necessary for thesereflectors to always be oriented directly onto the receiver pipe.Particularly because the reflectors must be tracked to follow the pathof the sun in order to achieve improved efficiency, precise setting andthe most ideal possible optical conditions are necessary for thegreatest possible efficiency of such a system.

In particular, it is problematic if—either due to imprecise orientationor due to imprecise tracking—the individual reflectors are not setoptimally or if the receiver is dirtied and thus an optimum transmissionof the light energy cannot be achieved. In the area of the receiver,which, among other things, has a cover that is also reflective on theinside, so that light guided past the receiver pipe is focused onceagain on the receiver pipe, the cleanliness of this mirror, on the onehand, but also the cleanliness of the glass pane enclosing the receiverpipe in the cover, through which the light from the reflectors fallsonto the receiver pipe, on the other hand, are essentially important.

In this context, it is known to fasten a measuring robot onto aframework on a receiver, so that the robot can be moved on theframework, along the receiver, and thus can resolve the incidence ofsolar energy through the primary reflectors as a function of location.However, it is problematic in this connection that the measuring robotin question can always be used on only one receiver.

Therefore the present invention is based on the task of creating a solarthermal energy system that ensures a high degree of effectiveness andalso otherwise overcomes the disadvantages of the prior art.

This is achieved by a solar thermal energy system according to thecharacteristics of the main claim as well as the other independentclaims 6 and 15. Further practical embodiments of the solar thermalenergy system can be derived from the dependent claims, in eachinstance.

According to the invention, a solar thermal energy system has ameasuring robot that can be set up along the receiver pipe so that itcan measure the radiation directed onto the receiver pipe. Such ameasuring robot is particularly advantageously assigned to the receivercover, on which the measuring robot can be disposed, without obstructingthe beam path to the receiver pipe itself in this connection. Inparticular, the measuring robot is capable of detecting the incidentradiation guided directly past the receiver pipe or the entire receiver,and thus determining whether and which of the reflectors are possiblyset incorrectly. A corresponding measuring robot can also be used forthe purpose of performing an initial adjustment of a newly set-up solarthermal energy system.

In operation, it is advantageous if the measuring robot, in eachinstance, can be moved on the receiver cover in its longitudinalexpanse, in that the measuring robot is equipped with a chassis. Areceiver cover usually has a polygonal shape, so that a defined travelsurface is created for the measuring robot. Using lateral stoppers andguide elements, the measuring robot can be disposed on a receiver insuch a way that it may be readily moved thereon. In particular, it isadvisable if the measuring robot is shaped in such a way that itencloses the receiver with shape fit, to a great extent, so that themeasuring robot is prevented from falling or rolling off the receiver.In this way, it is ensured that the measuring robot can also readilyprocess multiple receivers, one after the other.

In detail, such a measuring robot has at least one measuring arm that isequipped with photocells. On the basis of the response of individualones of the photocells on the measuring arm, the measuring robot candetermine by how much a reflector of the receiver deviates as the targetof the reflected incident sunlight. By means of a linear arrangement ofthe photocells on the measuring arm, a locally resolved distribution ofthe incident radiation on the receiver can be determined.

In a further embodiment, the measuring arm can be articulated onto themeasuring robot so as to pivot, so that a more precise determination ofthe beams or the beam bundles guided past the receiver can take place.In addition, in this way the measuring arm can be laid against themeasuring robot as needed, in order to be able to transport it in acompact transport form after use. If the measuring robot has pivotingmeasuring arms, the pivot position can be detected by the measuringrobot, so that it can be taken into consideration during a calculationof the beam density distribution around the receiver. In order toperform a simultaneous measurement of the reflectors disposed on bothsides of the receiver, it is easily possible to assign measuring arms tothe measuring robot on both sides.

However, it is also possible in this context to pivot the at least onepivot arm underneath the receiver, so that the radiation incident on thereceiver can be measured instead of the radiation conducted past thereceiver.

Additionally or alternatively, another measuring robot, which isequipped with an inclination sensor, can be used on the primarycollectors of the reflectors. This measuring robot detects theinclination of the reflector as a function of the location, in eachinstance, preferably using at least one inclination sensor. Thedeviation can then be determined by a reference value/actual valuecomparison and the orientation can be improved. This makes it possibleto carry out orientation measurements, which were only executed as spotchecks up to that time, in such a manner that they cover the area, andthus simplifies the adjustment procedure during the installation of asolar thermal energy system and its precision.

By means of the use of a suitable chassis, preferably consisting of aplurality of surface wheels for mounting the measuring robot on thereflector and a plurality of edge wheels for lateral guidance, themeasuring robot can be moved automatically, to a great extent, on thereflectors, and also easily switch over from one reflector to the nextreflector, which is adjacent in the longitudinal direction, by means ofthis construction, which is only set on.

In this connection, an adaptation of the shape of the measuring robot tothe primary collector can also take place, so that automatic movement ofthe measuring robot along this collector, as well, is also possible, ifapplicable.

In this connection, means for adjustment of the primary reflector, ineach instance, can also be assigned to the measuring robot, with whichmeans a precise adjustment of the reflector with regard to theinclination can take place, if applicable also in sections.

It is entirely possible to provide a measuring robot that can be usedboth on the receiver and on the reflector and has one or more chassissuitable for this purpose. In this case, such a measuring robot has notonly pivot arms having photocells, but also inclination sensors. Thisallows complete setting of the solar thermal energy system using only asingle measuring robot.

In order to create a system that functions as independently as possible,it is practical if the measuring robot is remote-controlled, whereby itis particularly advisable if the measuring robot follows programmingwhen performing its measurements, which programming permits it toprocess one receiver after another or one primary collector afteranother. In this connection, it is particularly practical if themeasuring robot can be remote-controlled from a central computer or fromcorresponding electronic means, whereby the remote control takes place,to particular advantage, in wireless manner, in other words particularlyby radio. A transmission of the measured values to the central computeralso takes place by radio.

A second aspect, which can also readily be used independent of themeasuring robots, to improve the efficiency of a solar thermal energysystem, is the addition of controlled ventilation, which takes place byway of a separate fan. In order to ensure the cleanliness of thereceiver, the receiver pipe is usually accommodated, in the area wherereflectors deflect the sunlight onto the receiver pipe, in a cavityformed by the receiver cover, which cavity is closed off on thereflector side by a glass pane. In this way, it is ensured that thesecondary reflector, which is also accommodated in the receiver, and thereceiver pipe do not get dusty and their optical properties are notimpaired. In addition, the glass pane that usually closes the cavity offin a downward direction is also somewhat protected from contamination inthis way. However, the situation is such that the cavity formed in thisway in the receiver is filled with a gas mixture, for example with air,and therefore also heats up and expands when the receiver is heated.Because this gas mixture is usually air, ventilation of the receiverwill therefore take place when it is heated, while an inflow of air willoccur during cooling. However, inflowing air can entrain dust into thecavity of the receiver, which can only be removed from there with greatdifficulty, and over time dirties the glass pane, the receiver pipe, andthe secondary reflector. Therefore, it is provided according to theinvention that the cavity is ventilated by way of a fan pipe, whereby anair filter, preferably a fine dust filter, is assigned to the fan pipe.In this way, no dust can penetrate into the interior of the cavity anddirty the glass pane or the receiver pipe.

In a practical further development, a blower can also be assigned to thefan pipe, which blower controls the air flow for ventilation.

The invention described above will be explained in greater detail in thefollowing, on the basis of an exemplary embodiment.

The figures show:

FIG. 1 a solar thermal energy system in a schematic representation,which cuts through the receiver and the reflectors transversely,

FIG. 2 a measuring robot set onto the receiver, in a cross-sectionalrepresentation,

FIG. 3 the receiver, in a detail representation, having a fan having afine dust filter, and

FIG. 4 a reflector having a measuring robot set on, in a perspectiverepresentation, at a slant from above.

FIG. 1 shows a solar thermal energy system 10, which essentially has anarray of reflectors 11 and a receiver 20. The receiver 20 is disposedelevated above the reflectors 11. Incident sunlight 12 is bundled by thereflectors 11 and directed onto the receiver 20. The reflected sunlight13 incident on the receiver 20 heats a receiver pipe 22 guided insidethe receiver 20, in which pipe a medium is guided, and energy can begenerated within the system by means of heating of the medium. In orderto ensure that the reflectors 11 are aligned exactly with the receiver20, a measuring robot 30 can be assigned to the solar thermal energysystem 10, which robot checks the orientation of the automaticallytracked reflectors 11 and can optimize the orientation, if necessary, onthe basis of its measured values.

FIG. 2 shows a measuring robot 30 of this type, which is set onto areceiver 20. For this purpose, the measuring robot 30 has a recess 35,which is adapted, in terms of its shape, to the receiver 20. A specificspacing is maintained between measuring robot 30 and receiver 20 bymeans of a chassis 34, which is assigned to the measuring robot 30, inorder to be able to move on the receiver 20 along its longitudinalexpanse. The measuring robot 30 has a measuring arm 31, in eachinstance, on both sides, which arm is disposed on the measuring robot 30so as to pivot, by way of a joint 32. Because of the joint 32, themeasuring arm 31 can be brought into various angle positions relative tothe measuring robot 30, so that the radiation deflected past thereceiver 20, which is reflected by the reflectors 11, can be detectedand measured in regard to the beam density distribution. Alternatively,the measuring arm 31 can also be pivoted between reflectors 11 andreceiver 20, in order to detect the incident radiation on the receiver20 instead of the radiation deflected past. Setting errors of thereflectors 11 can be found and remedied on the basis of the radiationconducted past the receiver 20. The efficiency of the overallconfiguration can be improved in this way. Such a measuring arm 31 isdisposed on both sides of the measuring robot 30, so that a measurementof the reflectors 11 can be performed simultaneously on both sides ofthe receiver 20. In order to achieve the most compact constructionpossible for transport after removal of the measuring robot 30 from thereceiver 20, the measuring arm 31 can be fixed in place on the sides ofthe measuring robot 30, in each instance, using a retainer 33. If themeasuring robot 30 is set onto a receiver 20, the measuring robot 30 canbe moved on the receiver cover 21 using the chassis 34. This can takeplace either by way of a remote control, for which purpose the measuringrobot 30 has an antenna 36, however, it is also possible to equip themeasuring robot 30 with programming, in such a way that it measures areceiver 20 completely automatically. In this connection, the datatransmission takes place between the measuring robot 30 and a centrallyset-up central computer, and is handled by way of the antenna 36, byradio.

FIG. 3 shows a further possibility for increasing the efficiency of asolar thermal energy system 1. For this purpose, it is provided tocompletely close off the cavity formed between the receiver cover 21 anda glass plate that closes off the receiver cover 21, so that no dust canpenetrate. The cavity thereby filled with air heats up, however, due tothe solar radiation that is conducted onto the receiver pipe 22 runninginside the cavity, using the reflectors. The air expands due to theheating and escapes by way of correspondingly provided ventilationopenings. During cooling of the receiver pipe 22 and thus also of theair inside the cavity, air is again drawn in, which may, however, carrydust particles into the interior of the receiver 20. For this purpose, afan pipe 41 and a fan, in connection with a fine dust filter, not shownin any detail, are assigned to the cavity, so that, on the one hand, theinflow can be regulated precisely using the fan and, on the other hand,the air flowing into the cavity can be freed of dust. It is therebyensured that the receiver 20, in particular the glass plate which closesoff the receiver 20 toward the bottom, is not contaminated by the dustthat is also drawn in.

During the measurement of the receiver, it is ascertained whether thelight reflected by the reflectors onto the receiver is incident on thereceiver, and how great the corresponding beam density is along thereceiver and its immediate surroundings. However, for accurate incidenceof the reflected light on the receiver, the inclination of the reflectormust also correspond to the specifications. A measuring robot 50according to FIG. 4 is therefore set onto a reflector 11 and equippedwith an inclination sensor, so that the measuring robot 50 can determinethe inclination of the reflector at any point of the reflector 11 alongits longitudinal expanse. Simultaneously, it compares the measuredvalues to the inclination predefined at the particular point, and canadapt the inclination of the reflector at the particular location, usingsuitable setting means. The current time is also taken intoconsideration in this connection, because the reflectors 11 are trackedaccording to the sun position, and therefore different degrees ofinclination are necessary at different points in time. Because of thechassis 52 also provided here, which predetermines a defined positionand travel direction, using edge wheels 54 and surface wheels 53, themeasuring robot 50 can also be moved on the reflector 11. Thisconstruction, which is only set on, additionally allows adjacentreflectors in the longitudinal direction to be moved to continuously, bybridging a spacing, because fixation on a specific reflector 11 by meansof corresponding structural measures, such as guide rails, etc., is notprovided.

A solar thermal energy system is thus described above, which is madesignificantly more efficient in that setting of the system can beperformed by means of a measuring robot, which can measure the incidentsunlight conducted past the receiver and/or the inclination of thereflectors, and permits better and more precise setting of thereflectors with significantly reduced effort, by means of a comparisonwith the corresponding reference values. Furthermore, an improvement ofthe efficiency is possible in that the receiver is prevented fromgetting dusty, using a filter-supported ventilation system.

LIST OF REFERENCE NUMERALS

10 solar thermal energy system

11 reflector

12 incident sunlight

13 reflected sunlight

20 receiver

21 receiver cover

22 receiver pipe

30 measuring robot

31 measuring arm

32 joint

33 retainer

34 chassis

35 recess

36 antenna

40 fan connector

41 fan pipe

42 blower

50 measuring robot

51 primary collector

52 chassis

53 surface wheels

54 edge wheels

1-18. (canceled)
 19. Solar thermal energy system having a plurality ofreflectors (11), which reflect incident sunlight (12) onto a receiver(20) mounted in elevated manner, whereby the receiver (20) has areceiver pipe (22) that is overlapped by a receiver cover (21), and ameasuring robot (30) is disposed on the receiver cover (21) formeasuring the beam density distribution of the sunlight (13) reflectedby the reflectors (11) in the area of the receiver pipe (22), whereinthe measuring robot (30) has a chassis (34) with which it is set ontothe receiver cover (21), whereby the measuring robot (30) can be movedin the longitudinal direction of the receiver cover (21) by means of thechassis (34).
 20. Solar thermal energy system according to claim 19,wherein at least one measuring arm (31), which has photocells for localresolution of the beam density distribution, is assigned to themeasuring robot (30).
 21. Solar thermal energy system according to claim20, wherein the measuring arm (31) is articulated onto the measuringrobot (30) so as to pivot, and the pivot position can be detected by themeasuring robot (30).
 22. Solar thermal energy system according to claim21, wherein the measuring arm (31) can be pivoted into a positionbetween receiver (20) and reflectors (11).
 23. Solar thermal energysystem according to claim 20, wherein at least one measuring arm (31) isassigned to the measuring robot (30), in each instance, on both sides.24. Solar thermal energy system having a plurality of reflectors (11),which reflect incident sunlight (12) onto a receiver (20) mounted inelevated manner, whereby the reflectors (11), in each instance, have aprimary collector (51) for reflecting the incident light onto thereceiver (20), wherein a measuring robot (50) for detection of theinclination of the reflector (11) is disposed on the primary reflector(51), which robot can be moved on the reflectors (11) by means of achassis (52).
 25. Solar thermal energy system according to claim 24,wherein the chassis (52) is formed, in each instance, by means of aplurality of surface wheels (53) for mounting the measuring robot (50)on the primary collector (51), and edge wheels (54) for laterallyguiding the measuring robot (50) in the longitudinal direction of thereflector (11).
 26. Solar thermal energy system according to claim 24,wherein the measuring robot (50) has an inclination sensor fordetermining the inclination of a primary collector (51).
 27. Solarthermal energy system according to claim 26, wherein the measuring robot(50) has means for adjustment, if necessary section by section, of theprimary collector in regard to its inclination.
 28. Solar thermal energysystem according to claim 19, wherein the measuring robot (30, 50) atleast partially encloses the receiver cover (21), or primary collector,with shape fit.
 29. Solar thermal energy system according to claim 19,wherein the measuring robot (30, 50) can be moved in remote-controlledmanner.
 30. Solar thermal energy system according to claim 19, whereinthe measuring robot (30, 50) is programmable for automatic execution ofmeasuring series.
 31. Solar thermal energy system according to claim 29,wherein data transmission takes place between a central computer foracquisition of data and, if applicable, remote control of the measuringrobot, and the measuring robot (30, 50), preferably in wireless manner.32. Solar thermal energy system according to claim 29, wherein anautonomous voltage source, preferably a rechargeable battery, isassigned to the measuring robot (30, 50).
 33. Solar thermal energysystem according to claim 19, wherein the measuring robot (30, 50) hasmeans for detecting the relative longitudinal displacement on thereceiver cover (21) or the primary collector (51).